Reference no: EM133808075

Electrical Installation - Inspection, Testing and Commissioning

Question Paper

Section A
Question 1. a) State the three elements of verification, as defined in B5 7672.

b) State three health and safety requirements placed on the person carrying out inspection and testing of an installation.

c) State the purpose of an inspection of an electrical installation, prior to testing.

d) An inspection of the provision of basic protection is to be carried out on an enclosure.
i) State two things that code IPXXB signified.

ii) Name the IP code which signifies protection from splashing from all directions.

e) List three pieces of information required on an electrical installation certificate in relation to the main switch/switch fuse/ circuit breaker/RCD.

Question 2. A socket outlet is to be inspected prior to the front plate being screed into place ready for testing.
Complete the table below, stating five items to be checked for compliance with BS 7671.

In each case, explain briefly what is being confirmed, and the human sense used

Item number What is being checked ? What is the check intended to confirm? Human sense used

Question 3. a)
i) State the name of the test method used to carry out an earth electrode resistance test using proprietary earth electrode tester.
ii) State the name of the instrument used to carry out ring final circuit test. Hire Experts Now!
iii) State the name of the instrument used to determine the prospective fault current at the origin of an installation.

b) List, in the correct sequence, the dead tests to be carried out on a radial socket outlet circuit

c) A 100 mA RCD is to be tested to confirm its suitability to provide fault protection on a TT installation
List the three elements to be carried out on the device.

d) A radial final circuit is supplied from a sub-distribution board at which the Z has been measured and recorded as 0.40 Ω.
The installation has a Z of 0.26Ω and the circuit has a measured (R1 + R1) of 0.34 Ω.
If the maximum permissible measured Zs allowed in the On-Site Guide for the circuit protective device is 0.70 Ω does this circuit comply with the requirements for automatic disconnection of supply?
Show all calculations.

e) State two physical factors, not including circuit faults, which could cause an increase in the resistance of any copy conductor.
In each case you must be specific about what change in the factor increases resistance.

Section B

*Question 4

As small engineering works is to be partially rewired, with a new three-phase distribution board installed in the refurbished workshop. This DB will supply general power and lighting in single core, none sheathed PVC insulated cable in conduit and trunking, as well as a number of circuits feeding three-phase machinery, installed in XLPE insulated SWA cable.

The supply and installation are on a 400/230 V, 4-wire, TN-C-S system, with a Z1 of 0.30 Ω and Ipp of 1.76 kA. All final circuits are protected by circuit breakers to BS EN 60898 AND RCBOs to BS EN 61009-1.

In addition, an electric vehicle charging point is to be installed in the car part. A risk assessment has determined that this particular circuit should be protected by its own earth electrode, making it a TT earthling arrangement.

The existing circuits in the main administrative part of the premises are also to be subjected to a periodic inspection and test at the same time. the building is around 40 years old and is of traditional brick and block construction with plaster finishes to external walls concealing flat twin and CPC cable for power and lights.

All testing is to be carried out at an ambient temperature of 20 °C
4. a)
i) List the three documents to be handed to the client on completion of the inspection and testing of the existing installation.

ii) On which documents is the maximum demand of the installation recorded?
iii) For how long should the client retain the documentation relation to this work?

iv) Following the periodic inspection and test, one circuit has had a section damaged cable replaced.
What document should be issued to certify this work is safe?

b) A test of insulation resistance is to be carried out on an existing low voltage lighting circuit.
ii) State the instrument to be used to perform the test.
ii) State the test voltage to be applied and the minimum acceptable insulation resistance value, including all units.

iii) Which insulation resistance test would not normally be carried out on a period inspection and test?

c) The polarity of the supply to the single-phase board in the office canteen area is to be verified.
i) State the instrument to be used.

ii) State two measurements to be made, including the terminals where the test probes must be applied, and the expected values for each test, to confirm the correct supply polarity.

*Question 5. Prior to the testing of the new electric vehicle charging point, an inspection must be carried out to confirm the correct selection and erection equipment.
a) State the names of three protective conductors which will be required in the installation generally and for this circuit.

b) On which document is the information about the main protective conductors recorded for this new work?

c) Devices are required for isolation and switching. For each of the following give two examples of suitable devices:
i) Isolation.

ii) Switching for mechanical maintenance.

iii) Functional switching.
iv) Emergency switching.

d) State three items of information related to circuit protective devices which are required to be entered on the schedule of circuit details

*Question 6. Describe, with the aid of fully labeled diagram, the earth fault pat for the electric vehicle charging equipment

Note: need only Question 4, 5 and 6.